J Pole Feed Point?

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Muxlow

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I have my j pole almost built and wonder what part i should solder the coax connecter to (would that be the feed point?)
And also wondering about the coax.. I saw some threads about having to pool it a few times and zip tie it to the pole?

http://www.hamuniverse.com/jpole.html

Thats the site i used to make the plans and such.. i typed in 866.0000 on the converter
I have a 9.7ft pipe, 3.2ft pipe and 2 3 ft pipes for cutting extra if needed.

Whats next? Perhaps someone can clear it up for me on how to make these connections for the connector and for the coax bit on how many turns to have it.
 

zz0468

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The feedpoint is at at dimension "c" on that web page. The diagram very clearly shows exactly how to connect to the antenna.

Coiling up the coax isn't necessary, but feel free to do it, if it makes you feel better. A couple of turns would be fine.
 

W6KRU

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Thats the site i used to make the plans and such.. i typed in 866.0000 on the converter I have a 9.7ft pipe, 3.2ft pipe and 2 3 ft pipes for cutting extra if needed.

Check that calculator again. For 866 MHz the dimensions are 9.7 inches, 3.2 inches, etc. not feet.
 

breadtrk

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I noticed the feet inch thing too, but it brought back something I learned many years ago about multiple wavelength antenna's. I wonder if those ideas apply at UHF?
 

Muxlow

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Sooo then it shouldnt be 9feet long? Seems to be rite at others iv seen.. and it starts with meters then feet then inches... and the 3 boxes. So i got my pipe cut to the middle box as if it were feet like it shows

Just the C and D box kinda confuse me

Also.. C would be the spot i put my coax or my so 232 i think it is?
And D is how far B should be away from A?
 
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W6KRU

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Sooo then it shouldnt be 9feet long? Seems to be rite at others iv seen.. and it starts with meters then feet then inches... and the 3 boxes. So i got my pipe cut to the middle box as if it were feet like it shows

Just the C and D box kinda confuse me

Also.. C would be the spot i put my coax or my so 232 i think it is?
And D is how far B should be away from A?

Look at that again dude. It shows feet, then inches, and then meters and it is misleading the way it is shown. 3.25 inches is a quarter wave at 800 MHz. The jpoles you are used to seeing are for vhf not 800 MHz.
 

zz0468

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No, the boxes are showing feet, inches, then meters, going from left to right. The "meters" label for the right most box is in the wrong position on the screen - crappy work on the part of the web page designer.
 

Muxlow

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Well fudge. Thats my problemo then.

Guess i have a wack load of pipe and i can make .. 3 more antennas.. vhf, uhf and a 800. woot:)

Thnx a bunch lads
 

Muxlow

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Was thinking.. since the j pole is not really for 800.. what would be a good base 800mhz antenna i can make out of all this copper pipe i have now?
 

W6KRU

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the dimensions of the pipe will change per freq as well. so you would need some skinny stuff.

I agree but I couldn't find a calculator for jpoles that allowed me to input the dia of the conductors. If I remember correctly, the diameter makes a relatively small difference compared to the length so it could be adjusted for if you worked slowly and made small adjustments.

You would gain bandwidth due to the larger conductors as a benefit.
 

breadtrk

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I plan to build a copper pipe jpole for 800 to take advantage of the bandwidth a larger diameter element inherently provides. I have some 1/4" and 3/8" copper left over from a home photo processing lab I installed at a friends house. I'll try to remember to dig through my receipts to find the source later today, it was online. I'm posting from my sound booth at the church right now and don't have access to them.
 
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